Conventionally, various types of devices for opening and closing a sliding door have been proposed. For example, a device for opening and closing a sliding door disclosed in Patent Document 1 includes a rail portion (90a), which is arranged on a base plate portion (90) and guides movement of a connection portion (1c) connected to the sliding door, a pulley (91), a sprocket (92), drive portions (93, 94, 95), which rotate the sprocket, and a drive tape (8), to which the connection portion (1c) is fixed. The drive tape is wrapped around the pulley and the sprocket. The device for opening and closing a sliding door is assembled in a portion below a door opening (2) formed in a lateral side of a vehicle body (4) in the vertical direction in a state in which members such as a drive portion are assembled in the base plate portion including the rail portion in advance.
Also, a device for opening and closing a sliding door disclosed in Patent Document 2 includes a drive pulley (12), idler pulleys (17, 18) arranged in the vicinity of the drive pulley, a driven pulley (15), a drive portion (13), which rotates the drive pulley, and a belt (16), which cooperates with a sliding door. The pulleys (12, 15, 17, 18), the drive portion (13), and the belt (16) are arranged in a step panel (14), on which a passenger steps when exiting or entering a vehicle. The belt is wrapped around the drive pulley and the driven pulley. The idler pulleys control the tension and path of the belt to prevent the belt from being disengaged (jumping) from the drive pulley. The device for opening and closing a sliding door is assembled in a portion below a door opening formed in a lateral side of a vehicle body in a vertical direction in a state in which members such as a drive portion are assembled in the step panel in advance. It has been proposed that flange portions (24) are provided on the idler pulleys to prevent the belt from hanging down, and an inner tapered surface (25) is formed in each of the flange portions to reduce rubbing noise of the belt.